272 "Wilt" or "Crown-Hot" Disease of Carnations 



During the seventeen days while this experiment was kept under 

 observation there was a rainfall of 4-19 ins., and the night previous 

 to placing the cultures in the soil -47 in. of rain fell: 2-19 ins. fell within 

 the first four days; 1-3 ins. between the 4th and 7th days. There 

 can be little doubt that the rainfall was responsible in certain measure 

 for the early appearance of the disease. Some of the diseased plants 

 showed the presence of the fungus as a whitish growth on the part 

 below the soil. 



3. The fungus in the tissues of the diseased plants. A transverse 

 section through the diseased area shows the fungus threads in the 

 xylem or wood. The wilting is undoubtedly due to the fungus blocking 

 up the vessels, decay is hastened by the entrance into the attacked 

 region of various saprophytic bacteria, though cases were observed 

 where bacteria were few and even altogether absent. 



The fungus is also abundant in the cells of the pith and is able 

 to invade the middle lamellae of the cells in the attacked region. The 

 fungus also permeates the cells of the cambium, phloem and cortex, 

 though in these regions it is less abundant than in the xylem and pith. 



4. Humidity as a factor influencing infection. In the field it has 

 usually been observed that the disease appears at its worst just after 

 the first rains. This was found to be the case also with plants inoculated 

 at the laboratory, and throws some light on the fact that plants inocu- 

 lated during the dry season in some cases took a month or more before 

 showing symptoms of the disease. 



B. Growth of the Fungus in the Laboratory. 

 I. Growth on Various Media at 25° C. 



Banana plugs. (PI. XXXVII, figs. 1, 2.) Inoculated 6. vii. 14. 

 9. vii. 14. Dense greyish, fluffy growth. 



13. vii. 14. Growth firm and compact, in places as much as 3-5 mm. 

 thick. Surface more fluffy than on potato. Chlamydo- 

 spores, both intercalary and apical, vary greatly in 

 size, 13'2-26-4/x diameter. 



20. vii. 14. Growth where it lies on cotton wool produces a region 

 about 2*3 mm. wide of a leaden grey (Plate 353. 3) 

 and above this a narrow, very bright yellow region 

 (Plate 35. 1). In places on the glass a honey yellow 

 (Plate 35. 4) is evident. No conidia. 



